Dear Economist,

Should I leave the lavatory seat down, as my wife demands? Or, with gravity on her side, should she be lowering it herself?

Michael Govind, Cirencester

-----------------------------------------------------------------------------------

Dear Michael,

Jay Pil Choi, a (male) economist at Michigan State University, has demonstrated what men find obvious and women seem unable to grasp: that the “status quo” rule (leave it how it was when you finished) is more efficient than the “down” rule (put it down afterwards) under most plausible assumptions. The reasoning is that the seat should be moved only when necessary - just before someone uses the lavatory.

If a man visits the lavatory twice in a row, the “status quo” rule saves the cost of lowering the seat when leaving only to raise it when returning. Choi also shows, using some fancy maths, that the “status quo” rule is still superior even if the inconvenience cost to your wife of moving the seat is nearly three times the inconvenience cost to you.

Why then, the continued controversy? Richard Harter, a (male) mathematician, has calculated the incremental costs of moving from bachelorhood or spinsterhood to connubial bliss. Since men sometimes need the seat down, they are used to bearing the cost of moving it. Women who live alone or with other women need never move the seat at all; therefore the incremental costs of moving to a mixed household are obvious.

Yet I feel that these thinkers have missed the bigger picture. Assume two types of man: the considerate gentleman and the selfish pig. It is famously difficult for women to distinguish them at first sight. Nevertheless it is easy for the gentleman to signal his “type” by returning the lavatory seat to the horizontal. This is a profitable lesson, and one that I learned early.

Questions to economist@ft.com